1. Field of Invention
The present invention relates to a light emitting diode, and more particularly to a light emitting diode driven by the alternating current.
2. Description of Related Art
Light emitting diodes have high reaction speeds, smaller volumes, lower power consumption, less heat radiation and extended lifetimes and the light emitting diodes have therefore gradually replaced conventional incandescent or halogen lamps. Applications for light emitting diodes, like the indication light for electronic apparatus, the back light source of the liquid crystal display (LCD) and the illuminator, are continually being extended as technology progresses.
However, the current inputted into the light emitting diode must be controlled precisely to maintain the radiation function. In addition, the light emitting diode is driven by a current such that it cannot be electrically connected with a low voltage source. The illumination is unstable when the current variation from the driving voltage is large. The light emitting diode is broken when the current exceeds the predetermined tolerant value.
The conventional light emitting diode is driven by a 3.5V direct current converted by a converter. Thus, the production cost is higher and the occupied volume is also large.
Refer to FIG. 1 and FIG. 2. FIG. 1 illustrates a circuit diagram of the conventional light emitting diode driven by the alternating current, and FIG. 2 illustrates an oscillogram of the sinusoidal signal detected from point A in FIG. 1. In this supply condition, the reverse bias damages the light emitting diode 700 or results in power-dissipation such that design flexibility and applications are limited. Take the bicycle lamp supplied by an alternating source for example, the light emitting diode cannot be directly driven by the generator.
As a result, there is a need for an alternating current light emitting diode without the converter to supply a stable direct current with sinusoidal signal.